Belt slip monitor

ABSTRACT

A belt slip monitor system and method configured to determine whether a belt coupled to a motor-generator is slipping based on operational states of first and second movable portions of the belt slip monitor, wherein the operational states of the first and second movable portions are dependent upon the tension in the belt.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 14/631,533, entitled “BELT SLIP MONITOR,” filed onFeb. 25, 2015. U.S. patent application Ser. No. 14/631,533 claimspriority to Great Britain Patent Application No 1404270.9, “Belt SlipMonitor,” filed Mar. 11, 2014. The entire contents of theabove-reference applications are hereby incorporated by reference intheir entirety for all purposes.

FIELD

This current application relates to a belt slip monitor for a belt, andin particular, but not exclusively, relates to a belt slip monitorconfigured to determine whether a belt coupled to a motor-generator isslipping based on operational states of first and second movableportions of the belt slip monitor.

BACKGROUND\SUMMARY

Motor-generators, such as a belt-driven integrated starter generator(ISG), may be used in assisting the operation of an engine by providingadditional torque, or by supplying electrical power to an electricalsystem of a vehicle. Belt tension of an accessory drive pulley of an ISGis typically monitored in order to reduce friction losses.

Belt tension may be monitored by way of a passive tension system, forexample. Alternatively, belt tension may be monitored by activelycontrolled tensioner devices to increase belt tension only when hightorque demands are made.

However, the inventors herein have recognized potential issues with suchsystems. Passive tensioning systems are set at a tension sufficient toavoid slip at a maximum operating torque, which may result in areduction of fuel efficiency. Actively controlled tensioner devices maybe less reliable and require electronic actuators which may be morecostly. Furthermore, spring-biased tensioning devices require additionalknowledge of a spring rate and may be prone to the effect of tolerances.

One potential approach to at least partially address some of the aboveissues includes a system and a method for a belt slip monitor whereinbelt tension and belt slippage may be monitored, and belt tension and/oroperational torque may be adjusted based on monitoring belt slippage.

In one example, a belt slip monitor for a belt coupled to amotor-generator, may comprise a first movable portion movable withrespect to the motor-generator, a second movable portion movably coupledto the first movable portion, the second movable portion being coupledto the belt such that operational states of the first and second movableportions of the belt slip monitor are dependent upon the tension in thebelt, a first sensor configured to determine the operational state ofthe first movable portion, and a second sensor configured to determinethe operational state of the second movable portion, wherein the beltslip monitor is configured to determine whether the belt is slippingbased on the operational state of the first and second movable portions.

In this way, the belt slip monitor, a passive tensioning device, maydetect slip both when the ISG transmits torque to the system, andremoves torque from the system. Further, the belt slip monitor systemmay adjust operational torque, and thereby belt tension, so that fuelefficiency may increase, unlike known passive tensioner devices thatmust operate at a high tension.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example schematic diagram of one cylinder of multi-cylinderengine of a motor vehicle comprising a control system;

FIG. 2A shows a belt slip monitor for a belt coupled to a motorgenerator pulley, a crankshaft pullet and an accessory pulley;

FIG. 2B shows a belt slip monitor for a belt;

FIG. 2C shows an alternative embodiment of a belt slip monitor;

FIG. 3A shows the belt slip monitor comprising a first and second anglesensor;

FIG. 3B shows the belt slip monitor comprising a first and second straingauge;

FIG. 4A shows an example mode of operation of the belt slip monitor, inwhich the motor-generator is operating as a motor and the belt is notslipping;

FIG. 4B shows the example mode of operation of the belt slip monitor, inwhich the motor-generator is operating as a motor and the belt isslipping;

FIG. 5A shows another example mode of operation of the belt slipmonitor, in which the motor-generator is operating as a generator andthe belt is not slipping; and

FIG. 5B shows the other example mode of operation of the belt slipmonitor, in which the motor-generator is operating as a generator andthe belt is slipping;

FIG. 6 shows an example method flowchart for monitoring belt slippagevia a belt slip monitor.

DETAILED DESCRIPTION

Motor-generators may be used to selectively assist in the operation ofan engine or to supply electrical power to an electrical system of theengine and/or a vehicle. Motor-generators may be used therefore as partof parallel hybrid technology. As vehicle manufacturers move toincorporate increasing levels of hybrid technology into their products,the alternator of the engine may be replaced by the motor-generator, forexample an Integrated Starter Generator (ISG), on an accessory beltdrive system.

By replacing the alternator with the ISG, regenerative braking energymay be captured and the ISG may provide torque assist during periods ofhigh-load operation. The ISG may also enable faster engine restartsduring start-stop events. Whilst a standard alternator system onlyrequires torque transmission in a single direction, an ISG requirestorque transmission in both directions, with increased levels of torquetransmission compared to the standard alternator system. Higher levelsof torque transmission mean that the belt tension must be set for thetoughest use case, for example a water-wading scenario during which thebelt friction is reduced. However, accounting for such a scenario canresult in a high tension in the belt, which will result in a reducedfuel economy.

In order to minimize the friction losses of the accessory drive beltsystem, it is desirable to maintain as low a belt tension wheneverpossible. It is known to provide adjustable tensioner devices toincrease the belt tension only when high torque demands are made.However, such actively controlled tensioner devices may be lessreliable.

The present current application seeks to address these issues. Accordingto an aspect of the present application there is provided a belt slipmonitor for a belt coupled to a motor-generator, the belt slip monitorcomprising: a first movable portion movable with respect to themotor-generator; a second movable portion movably coupled to the firstmovable portion, the second movable portion being coupled to the beltsuch that operational states of the first and second movable portions ofthe belt slip monitor may be dependent upon the tension in the belt; anda first sensor configured to determine the operational state, forexample position, of the first movable portion. The belt slip monitormay comprise a second sensor configured to determine the operationalstate, for example position, of the second movable portion. The beltslip monitor may be configured to determine whether the belt is slippingbased on the operational state of the first and/or second movableportions.

The belt slip monitor may be configured to determine if the belt coupledto the motor-generator is slipping, for example due to the operationaltorque of the motor-generator and/or any other device associated withthe belt, such as a crankshaft pulley or an accessory device pulley. Thebelt slip monitor may comprise one or more control devices configured toadjust the operational torque of the motor-generator in response to theoperational state of the first and/or second movable portions of thebelt slip monitor such that the belt no longer slips.

The second movable portion may be coupled to the belt at a first end ofthe second movable portion. The second movable portion may be coupled tothe belt at a second end of the second movable portion. The first andsecond ends of the second movable portion may be coupled to the belteither side of the motor-generator.

The tension in the belt may be dependent upon the operational torque ofthe motor-generator. The belt slip monitor may be configured to apply apretension to the belt.

The first movable portion may be coupled to an anchor point that issubstantially fixed relative to the movement of the motor-generator. Thefirst and second movable portions may be configured to move with respectto the belt. The first and second movable portions may be rotationallyand/or slidably movable. The first and second movable portions may berotationally and/or slidably coupled to each other. The second movableportion may comprise one or more pulleys for engaging the belt. Thefirst and/or second movable portions may be coupled to an engine of avehicle.

The first and second sensors may comprise angle sensors configured todetermine the angular position of the first and/or second movableportions. The first and second sensors may comprise strain gaugesconfigured to determine the strain in the first and/or second movableportions. At least a portion of the first sensor may be attachable tothe first movable portion. At least a portion of the first sensor may beattachable to the engine, vehicle or any other supporting structure. Atleast a portion of the second sensor may be attachable to the secondmovable portion. At least a portion of the second sensor may beattachable to the first movable portion.

The motor-generator may comprise an integrated starter-generator. Thebelt may be an accessory drive belt, for example a serpentine belt.

An engine may be provided comprising one or more of the belt slipmonitors according to the present application.

A vehicle, such as a motor vehicle, may be provided comprising one ormore of the belt slip monitors and/or the engine according to thepresent application.

The engine and/or the vehicle may comprise one or more control devicesconfigured to adjust the operational torque of the motor-generator.

According to another aspect of the present application there is provideda method of monitoring the slip of a belt coupled to a motor-generatorusing a belt slip monitor, the method comprising: determining theoperational state of a first movable portion of the belt slip monitorusing a first sensor, wherein the first movable portion is movable withrespect to the motor-generator; determining the operational state of asecond movable portion of the belt slip monitor using a second sensor,wherein the second movable portion is movably coupled to the firstmovable portion, the second movable portion being coupled to the beltsuch that the operational states of the first and second movableportions of the belt slip monitor may be dependent upon the tension inthe belt; and determining whether the belt is slipping based on theoperational state of the first and second movable portions.

The tension in the belt may be dependent upon the operational torque ofthe motor-generator. The method may comprise determining if the beltcoupled to the motor-generator is slipping, for example due to theoperational torque of the motor-generator.

The method may comprise adjusting the operational torque of themotor-generator in response to the operational state of the first and/orsecond movable portions of the belt slip monitor such that the belt doesnot slip.

The method may comprise corroborating that the belt is slipping bycomparing the outputs from the first and second sensors.

The method may comprise monitoring belt slip and implementing acountermeasure to reduce torque demand through the belt if slip isdetected. For example, the torque demand though the belt may be reducedby adjusting the operational torque of the motor-generator, the engineand/or one or more accessory devices. Reducing the torque demand throughthe belt may result in a reduced belt tension. Belt slip may bemonitored by way of a passive tensioning device. Example countermeasuresmay include: inhibiting start-stop events; using the motor-generatorand/or a starter motor of the engine to assist cranking the engine;inhibiting ISG functions that transmit high torque through the belt;and/or providing a suitable indication to the driver when there is aproblem with the belt. In this manner, the belt tension may be minimizedacross a range of operational conditions of the ISG.

The present application also provides software, such as a computerprogram or a computer program product for carrying out any of themethods described herein, and a computer readable medium having storedthereon a program for carrying out any of the methods described herein.A computer program embodying the present application may be stored on acomputer-readable medium, or it could, for example, be in the form of asignal such as a downloadable data signal provided from an Internetwebsite, or it could be in any other form.

Referring to FIG. 1, a schematic diagram showing one cylinder ofmulti-cylinder engine 10, which may be included in a propulsion systemof an automobile, is illustrated. Engine 10 may be controlled at leastpartially by a control system including controller 20 and by input froma vehicle operator 132 via an input device 130. In this example, inputdevice 130 includes an accelerator pedal and a pedal position sensor 134for generating a proportional pedal position signal PP. Combustionchamber (i.e., cylinder) 71 of engine 10 may include combustion chamberwalls 72 with piston 76 positioned therein. Piston 76 may be coupled tocrankshaft 80 so that reciprocating motion of the piston is translatedinto rotational motion of the crankshaft. Crankshaft 80 may be coupledto at least one drive wheel of a vehicle via an intermediatetransmission system. Further, a starter motor may be coupled tocrankshaft 80 via a flywheel to enable a starting operation of engine10. For example, an ISG may be coupled to the crankshaft via a FEADbelt, which may have a passive tensioner as depicted in FIGS. 2A-3B.

Combustion chamber 71 may receive intake air from intake manifold 44 viaintake passage 42 and may exhaust combustion gases via exhaust passage48. Intake manifold 44 and exhaust passage 48 can selectivelycommunicate with combustion chamber 71 via respective intake valve 52and exhaust valve 54. In some embodiments, combustion chamber 71 mayinclude two or more intake valves and/or two or more exhaust valves.

In this example, intake valve 52 and exhaust valves 54 may be controlledby cam actuation via respective cam actuation systems 51 and 53. Camactuation systems 51 and 53 may each include one or more cams and mayutilize one or more of cam profile switching (CPS), variable cam timing(VCT), variable valve timing (VVT) and/or variable valve lift (VVL)systems that may be operated by controller 20 to vary valve operation.The position of intake valve 52 and exhaust valve 54 may be determinedby position sensors 55 and 57, respectively. In alternative embodiments,intake valve 52 and/or exhaust valve 54 may be controlled by electricvalve actuation. For example, cylinder 71 may alternatively include anintake valve controlled via electric valve actuation and an exhaustvalve controlled via cam actuation including CPS and/or VCT systems.

Fuel injector 66 is shown arranged in intake manifold 44 in aconfiguration that provides what is known as port injection of fuel intothe intake port upstream of combustion chamber 71. Fuel injector 66 mayinject fuel in proportion to the pulse width of signal FPW received fromcontroller 20 via electronic driver 68. Fuel may be delivered to fuelinjector 66 by a fuel system (not shown) including a fuel tank, a fuelpump, and a fuel rail. In some embodiments, combustion chamber 71 mayalternatively or additionally include a fuel injector coupled directlyto combustion chamber 71 for injecting fuel directly therein, in amanner known as direct injection.

Intake passage 42 may include a throttle 62 having a throttle plate 64.In this particular example, the position of throttle plate 64 may bevaried by controller 20 via a signal provided to an electric motor oractuator included with throttle 62, a configuration that is commonlyreferred to as electronic throttle control (ETC). In this manner,throttle 62 may be operated to vary the intake air provided tocombustion chamber 71 among other engine cylinders. The position ofthrottle plate 64 may be provided to controller 20 by throttle positionsignal TP. Intake passage 42 may include a mass air flow sensor 120 anda manifold air pressure sensor 122 for providing respective signals MAFand MAP to controller 20.

Ignition system 88 can provide an ignition spark to combustion chamber71 via spark plug 92 in response to spark advance signal SA fromcontroller 20, under select operating modes. Though spark ignitioncomponents are shown, in some embodiments, combustion chamber 71 or oneor more other combustion chambers of engine 10 may be operated in acompression ignition mode, with or without an ignition spark.

Exhaust gas sensor 126 is shown coupled to exhaust passage 48 upstreamof emission control device 70. Sensor 126 may be any suitable sensor forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or COsensor. Emission control device 70 is shown arranged along exhaustpassage 48 downstream of exhaust gas sensor 126. Device 70 may be athree way catalyst (TWC), NOx trap, various other emission controldevices, or combinations thereof. In some embodiments, during operationof engine 10, emission control device 70 may be periodically reset byoperating at least one cylinder of the engine within a particularair/fuel ratio.

Controller 20 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 102, input/output ports 21, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 106 in this particular example, random access memory 108,keep alive memory 110, and a data bus. Controller 20 may receive varioussignals from sensors coupled to engine 10, in addition to those signalspreviously discussed, including measurement of inducted mass air flow(MAF) from mass air flow sensor 120; engine coolant temperature (ECT)from temperature sensor 112 coupled to cooling sleeve 114; a profileignition pickup signal (PIP) from Hall effect sensor 118 (or other type)coupled to crankshaft 80; throttle position (TP) from a throttleposition sensor; and absolute manifold pressure signal, MAP, from sensor122 and from sensors on the passive tensioner device on the FEAD belt,as shown in FIGS. 3A and 3B. Engine speed signal, RPM, may be generatedby controller 20 from signal PIP. Manifold pressure signal MAP from amanifold pressure sensor may be used to provide an indication of vacuum,or pressure, in the intake manifold. Note that various combinations ofthe above sensors may be used, such as a MAF sensor without a MAPsensor, or vice versa. During stoichiometric operation, the MAP sensorcan give an indication of engine torque. Further, this sensor, alongwith the detected engine speed, can provide an estimate of charge(including air) inducted into the cylinder. In one example, sensor 118,which is also used as an engine speed sensor, may produce apredetermined number of equally spaced pulses every revolution of thecrankshaft.

Storage medium read-only memory 106 can be programmed with computerreadable data representing instructions executable by processor 20 forperforming the methods described below as well as other variants thatare anticipated but not specifically listed.

As described above, FIG. 1 shows only one cylinder of a multi-cylinderengine, and that each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector, spark plug, etc.

FIG. 2A shows a belt slip monitor 200 for a belt 202 coupled to amotor-generator pulley 204, for example a pulley of an integratedstarter-generator of an engine. The belt slip monitor 200 comprises afirst movable portion 206 that is movable with respect to themotor-generator 204 and second movable portion 208 movably coupled tothe first movable portion 206. The second movable portion 208 is coupledto the belt 202 such that operational states of the first and secondmovable portions 206, 208 of the belt slip monitor 200 are dependentupon the tension in the belt 202.

In the example shown in FIG. 2A, the belt 202 is an accessory drivebelt, for example a serpentine belt or a FEAD belt, that is coupled tothe motor-generator pulley 204, a crankshaft pulley 210 and an accessorydevice pulley 212, for example a pump pulley or a compressor pulley.Although not shown, further accessory devices and pulleys may be coupledto the belt 202. The second movable portion 208 of the belt slip monitor200 is coupled to the belt 202 at a first end 208 a on a first side 226of the motor-generator pulley 204 and at a second end 208 b on a secondside 228 of the motor-generator pulley 204. The second movable portion208 is coupled to the belt 202 by way of pulleys 214 configured toengage the belt 202 at the first and second ends 208 a, 208 b of thesecond movable portion 208. In an alternative example, the first andsecond ends 208 a, 208 b of the second movable portion 208 may becoupled to the belt on either side of the crankshaft pulley 210, theaccessory device pulley 212 or any other appropriate pulley for which itis desirable to monitor belt slip.

In the example shown in FIG. 2A, the first movable portion 206 iscoupled to an anchor point 216 that is fixed relative to themotor-generator pulley 204. The anchor point 216 may comprise a portionof the engine and/or a portion of a vehicle. The first movable portion206 is rotationally coupled to the anchor point 216. The second movableportion 208 is rotationally coupled to the first movable portion 206.The first and second movable portions 206, 208 may be thus configured tomove with respect to the belt 202. However, in an alternative example,the first and second movable portions 206, 208 may be rotationallyand/or slidably movable with respect to the belt 202 and rotationallyand/or slidably coupled to each other.

The first and/or second movable portions 206, 208 may be substantiallyelongate. The first movable portion 206 may be provided with a firstcoupling at a first end for rotatably coupling the first movable portion206 to the anchor point 216. The first movable portion 206 may beprovided with a second coupling at a second end for rotatably couplingthe first movable portion 206 to the second movable portion 208. Thesecond movable portion 208 may be provided with a third coupling betweenfirst and second ends of the second movable portion 208. The thirdcoupling may be provided approximately midway between the first andsecond ends of the second movable portion 208. The third coupling mayengage the second coupling of the first movable portion 206 to permitrelative rotation between the first and second movable portions 206,208.

The rotatable couplings between the anchor point 216 and the firstmovable portion 206 and/or between the first movable portion 206 and thesecond movable portion 208 may or may not be resisted. For example, inthe case of the rotatable couplings being resisted, the rotatablecouplings may be provided with a resilient element, such as a coilspring and/or any other resilient element. Such resistance to therotation of the first and/or second movable portions 206, 208 may applyin either rotational direction and may act to return the first and/orsecond movable portions 206, 208 to a default position, for example asshown in FIG. 2A.

The belt slip monitor 200 may be configured to apply a pretension to thebelt 202, for example by virtue of the length of the first and secondmovable portions 206, 208, such that when the engine is switched off,the tension in the belt 202 consists solely of the static pretension. Insuch a situation, the tension in the belt 202 on the first side 226 ofthe motor-generator pulley 204 is substantially equal to the tension inthe belt 202 on the second side 228 of the motor-generator pulley 204and the first and second movable portions 206, 208 are in firstoperational states, as shown in FIG. 2A. In another example, the beltslip monitor 200 may be biased by one or more biasing elements, forexample a spring, such that the pretension applied to the belt 202 bythe belt slip monitor 200 is dependent upon the configuration of thebiasing elements.

In the examples given below, the operational states of the first andsecond movable portions 206, 208 relate to the angular position ofand/or the strain in the first and second movable portions 206, 208.However, it may be appreciated that the operational states of the firstand second movable portions 206, 208 may relate to any change inposition of the first and second movable portions 206, 208, for examplerotational and or translational changes in position, or indeed anyparameter of the first and second movable portions 206, 208 that may beaffected by the tension in the belt 202.

The belt slip monitor 200 comprises a first sensor configured todetermine the operational state of the first movable portion 206 and asecond sensor configured to determine the operational state of thesecond movable portion 208. In this manner, the belt slip monitor 200 isconfigured to determine whether the belt 202 is slipping based onoperational states of the first and second movable portions 206, 208.

Turning to FIG. 2B, an additional example of anchor point 216 of FIG. 2Ais shown. Anchor point 216 is rotatably fixed to a cylinder block, forexample. First movable portion 206 therefore pivots with respect to theanchor point 216 which is rotatably fixed to the cylinder block. Secondmovable portion 208 may be rotatably fixed to first movable portion 206about pivot 209, but not to the cylinder block. Therefore, secondmovable portion 208 may pivot with respect to first movable portion 206.Further, second movable portion 208 is coupled to belt 202 by way ofpulleys 214, and is not fixed to the cylinder block. In one example,pulley 214 on first side 226 is rotatably fixed to second movableportion 208 by pivot 217 a so that it moves relative to the block but isnot fixed to it. Pivots 217 a and 217 b, as well as the pivot betweenthe arm 208 and arm 206 may each float relative to the block, in thatthey are not rotatably fixed to the block. Pulley 214 on second side 228is rotatably fixed to second movable portion 208 about a pivot 217 b.

FIG. 2C depicts an alternative embodiment of belt slip monitor 200. Inthis example, the belt slip monitor comprises two rollers. One rotatableroller is located on first side 226 and the second rotatable roller islocated on the second side 228. Further, the rollers are attached via atensioner arm 211 such that the arm may be pretensioned to providecompression forces on the band. The tensioner arm may be elongate,shaped with a rectangular cross-section and formed of metal, in oneexample. The rotatable rollers may be in direct contact with the beltsuch that the rollers move in the direction of arrows 213 based on atension of the belt. It may be appreciated that the rollers are notfixed to the block but rather float relative to the block. Further, thebelt slip monitor may comprise a first sensor configured to determinethe position and/or operational state of the first roller, and a secondsensor configured to determine the position and/or operational state ofthe second roller. In this manner, the belt slip monitor 200 isconfigured to determine whether the belt 202 is slipping based onoperational states and/or positions of the first and second movablerollers 209 a and 209 b.

In the example shown in FIG. 3A, the first and second sensors comprisefirst and second angle sensors 218 a, 220 a configured to determine theangular position of the first and second movable portions 206, 208respectively. The first angle sensor 218 a is configured to determinethe angular position of the first movable portion 206 with respect tothe anchor point 216 and the second angle sensor 220 a is configured todetermine the angular position of the second movable portion 208 withrespect to the first movable portion 206.

In the example shown in FIG. 3B, the first and second sensors comprisefirst and second strain gauges 218 b, 220 b configured to determine thestrain in the first and second movable portions 206, 208 respectively.It may be appreciated, however, that in an alternative example the beltslip monitor 200 may comprise any number of angle sensors and/or straingauges configured to determine the operational states of the first andsecond movable portions 206, 208. In this manner, the belt slip monitor200 may be configured to determine whether the belt 202 is slippingbased on the angular positions of and/or the strain in the first andsecond movable portions 206, 208.

In the examples shown in FIGS. 3A and 3B, the first and second sensorsare attached to the first and second movable portions 206, 208respectively. However, it may be appreciated that first and secondsensors may be attached to any portion of the belt slip monitor 200, aportion of the engine and/or a portion of the vehicle such that thefirst and second sensors are configured to determine the operationalstates of the first and second movable portions 206, 208. For example,the angle sensors 218 a, 220 a may comprise a portion on the respectivemovable portion and a further portion in a fixed position relative tothe anchor point 216 or the first movable portion 206. The respectiveangle sensor movable portions may together determine the angle of thefirst and second movable portions 206, 208.

The belt slip monitor 200 may be configured to determine if the belt 202coupled to the motor-generator pulley 204 is slipping, for example dueto the operational torque of the motor-generator. For example, when themotor-generator functions as a motor, e.g. as a starter motor of theengine, the motor-generator is configured to drive the belt 202. Whenmotor-generator functions as the motor, the motor-generator applies adriving torque to the belt 202 in the same direction as a torque inputto the belt 202 by the crankshaft pulley 210 when the motor issupplementing drive produced by the engine. In another example, themotor-generator applies a driving torque to the belt 202 in the oppositedirection to a resistive torque applied by the crankshaft pulley 210when the motor is starting the engine. In such a circumstance, the belt202 will slip if the operational torque of the motor-generator, e.g. thedriving torque applied by the motor-generator, is sufficiently large.Conversely, when the motor-generator functions as a generator, e.g. asan alternator of the engine, the motor-generator is configured to bedriven by the belt 202. When the motor-generator functions as thegenerator, the motor-generator applies a resistive torque to the belt202 in the opposite direction to the torque input to the belt 202 by thecrankshaft pulley 210. In such a circumstance, the belt 202 will slip ifthe operational torque of the motor-generator, e.g., the resistivetorque applied to the belt 202 by the motor-generator, is sufficientlylarge. The belt 202 may also slip if a torque (resistive or otherwise)applied by the crankshaft pulley 210 is sufficiently large.

When the belt 202 slips, the tension on the belt 202 is significantlyreduced. Accordingly, the belt may return to substantially the positionshown in FIG. 2A. The return of the belt 202 to this position, which isindicative of belt slip occurring, may be detected substantially by thefirst and second movable portions 206, 208.

The belt slip monitor may comprise one or more control devicesconfigured to adjust the operational torque of the motor-generator inresponse to the operational state of the first and/or second movableportions 206, 208 such that the belt 202 does not slip. For example,when motor-generator functions as the motor, the control device may beconfigured to reduce the driving torque of the motor-generator if thedriving torque applied by the motor-generator in order to drive the belt202 is sufficiently large to cause the belt 202 to slip. In anotherexample, when the motor-generator functions as the generator the controldevice may be configured to reduce the resistive torque of themotor-generator if the resistive torque applied to the belt 202 by themotor-generator is sufficiently large to cause the belt 202 to slip.

In another example of the present application there is provided a methodof monitoring the slip of the belt 202 coupled to the motor-generatorusing the belt slip monitor 200. The method comprises determining theoperational state of the first movable portion 206 of the belt slipmonitor 200 using the first sensor, wherein the first movable portion206 is movable with respect to the motor-generator. The method furthercomprises determining the operational state of the second movableportion 208 of the belt slip monitor 200 using the second sensor,wherein the second movable portion 208 is movably coupled to the firstmovable portion 206. The second movable portion 208 is coupled to thebelt 202 such that the operational states of the first and secondmovable portions 206, 208 of the belt slip monitor 200 are dependentupon the tension in the belt 202. The method further comprisesdetermining whether the belt 202 is slipping based on the operationalstate of the first and second movable portions 206, 208.

The tension in the belt 202 may be dependent upon the operational torqueof the motor-generator. In this manner, the method may further comprisedetermining if the belt 202 coupled to the motor-generator is slippingdue to the operational torque of the motor-generator.

The method may further comprise adjusting the operational torque of themotor-generator in response to the operational state of the first and/orsecond movable portions 206, 208 of the belt slip monitor 200 such thatthe belt 202 does not slip. For example, the method may comprisesupplying one or more control signals to the control device for thepurpose of adjusting the operational torque of the motor-generator.

In a further example, the method may comprise corroborating that thebelt 202 is slipping by comparing the outputs from the first and secondsensors. For example, the tension in the belt may fluctuate, e.g., dueto variations in the operational torque of the engine and/or due tovibration of the engine during normal operation. Such fluctuations mayresult in a false determination of belt slip. However, by monitoringoutputs from both the first and second sensors, the likelihood of such afalse determination may be reduced. The first and second movableportions 206, 208 move in different directions and may therefore respondto fluctuations of different frequencies and/or amplitudes. Accordingly,by corroborating the signals from the first and second movable portions206, 208, the likelihood of false slip determination is reduced.Furthermore, in a scenario where a sensor is malfunctioning, acomparison between two sensor outputs may be used to check that the belt202 is slipping. The method may comprise comparing the outputs from thefirst and second sensors against a predetermined set of values to ensurethat the outputs from the first or second sensors are in fact indicativeof the belt 202 slipping. Furthermore, the provision of more than onesensor provides a redundancy in the event that there is a failure of oneof the sensors.

In addition, outputs from the first and/or second sensors may becorroborated against the operational state of the motor-generator, forexample if the motor-generator is disengaged and is neither generatingnor receiving torque, since such a state may also result in a falsedetermination of slip.

First Example Mode of Operation for the Belt Slip Monitor

FIGS. 4A and 4B depict an example mode of operation of the belt slipmonitor 100, in which the motor-generator is operating as a motor. FIG.4A shows the belt 202 being driven by the crankshaft pulley 210 suchthat the crankshaft pulley 210, the accessory device pulley 212 and themotor-generator pulley 204 are all rotating. In addition to the torque(indicated by arrow 222) applied to the belt 202 by the crankshaftpulley 210, the motor-generator is configured to apply a secondarytorque (indicated by arrow 224) to assist in driving the belt 202, forexample when the torque requirements of one or more accessory devicescoupled to belt 202 are large and/or when the load on the engine ishigh. As a result of the secondary torque 224 applied to the belt 202,the tension in the belt 202 on the first side 226 of the motor-generatorpulley 204 is greater than the tension in the belt 202 on the secondside 228 of the motor-generator pulley 204. As a consequence of thedifference between the tensions in the belt 202 on the first and secondsides 226, 228 of the motor-generator pulley 204, the first movableportion 206 rotates about the anchor point 216 and the second movableportion 208 rotates relative to the first movable portion, for examplein the opposite direction to the first movable portion 206. In thismanner, when the secondary torque 224 is applied to the belt 202 by themotor-generator pulley 204, the first and second movable portions 206,208 of the belt slip monitor 200 are in second operational states.

In a similar manner to FIG. 4A, FIG. 4B shows the belt 202 being drivenby the crankshaft pulley 210. However, in FIG. 4B, an increasedsecondary torque (indicated by arrow 224′) is provided by themotor-generator. The increased secondary torque 224′ is sufficient tocause the belt 202 to slip over the motor-generator pulley 204 and, as aresult, torque is not transferred from the motor-generator pulley 204 tothe belt 202. Consequent to the belt 202 slipping, the tension in thebelt 202 on the first side 226 of the motor-generator pulley 204 issubstantially equal to the tension in the belt 202 on the second side228 of the motor-generator pulley 204 and the first and second movableportions 206, 208 are in first operational states. In this manner, theoperational states of the first and second movable portions 206, 208 ofthe belt slip monitor 200 are dependent upon the operational torque ofthe motor-generator and, therefore, the tension in the belt 202 coupledto the motor-generator pulley 204.

In the example shown in FIGS. 4A and 4B, therefore, the first and secondsensors are configured to determine a change between the first andsecond operational states of the first and second movable portions 206,208 consequent to an increase in the driving torque 224, 224′ providedby the motor-generator.

Second Example Mode of Operation for the Belt Slip Monitor

FIGS. 5A and 5B depict an example mode of operation of the belt slipmonitor 200, in which the motor-generator is operating as a generator.FIG. 5A shows the belt 202 being driven by the crankshaft pulley 210such that the crankshaft pulley 210, the accessory device pulley 212 andthe motor-generator pulley 204 are all rotating. In the example shown inFIG. 5A, the motor-generator, when acting as a generator, is configuredto apply a resistive torque to the belt (indicated by arrow 230). As aresult of the resistive torque 230 applied to the belt 202, the tensionin the belt 202 on the first side 226 of the motor-generator pulley 204is less than the tension in the belt 202 on the second side 228 of themotor-generator pulley 204. As a consequence of the difference betweenthe tensions in the belt 202 on the first and second sides 226, 228 ofthe motor-generator pulley 204, the first movable portion 206 rotatesabout the anchor point 216 and the second movable portion 208 rotatesrelative to the first movable portion, for example in the oppositedirection to the first movable portion 206. In this manner, when theresistive torque is applied to the belt 202 by the motor-generatorpulley 204, the first and second movable portions 206, 208 of the beltslip monitor 200 are in third operational states.

In a similar manner to FIG. 5A, FIG. 5B shows the belt 202 being drivenby the crankshaft pulley 210. However, in FIG. 5B, an increasedresistive torque (indicated by arrow 230′) is provided by themotor-generator. The increased resistive torque 230′ is sufficient tocause the motor-generator to stall and the belt 202 to slip over themotor-generator pulley 204. As a result of the belt 202 slipping, thetension in the belt 202 on the first side 226 of the motor-generatorpulley 204 is substantially equal to the tension in the belt 202 on thesecond side 228 of the motor-generator pulley 204 and the first andsecond movable portions 206, 208 are in first operational states. Inthis manner, the operational states of the first and second movableportions 206, 208 of the belt slip monitor 200 may be dependent upon theoperational torque of the motor-generator and, therefore, the tension inthe belt 202 coupled to the motor-generator pulley 204.

In the example shown in FIGS. 5A and 5B, therefore, the first and secondsensors may be configured to determine a change between the first andthird operational states of the first and second movable portions 206,208 consequent to an increase in the resistive torque 230, 230′ providedby the motor-generator.

In the examples shown in FIGS. 4A to 5B, the change in operationalstates of the first and second movable portions 206, 208 is determinedby the first and second angle sensors 218 a, 220 a (as shown in FIG.3A). In an alternative example, however, the change in operationalstates of the first and second movable portions 206, 208 may bedetermined by the strain gauges 218 b, 220 b (as shown in FIG. 3B), orindeed any appropriate sensor, for example a proximity sensor, capableof determining the operational states of the first and second movableportions 206, 208. It is appreciated, therefore, that the belt slipmonitor 200, as prescribed by the present application, does not requirehigh resolution angular speed sensing of rotational components, such aspulleys or gears, in order to identify belt slip.

In the example shown in FIGS. 4A to 5B, the first and second sensors areconfigured to determine a change from the second and/or thirdoperational states of the first and second movable portions 206, 208, tothe first operational state of the first and second movable portions206, 208, consequent to a sufficiently large increase in the operationaltorque of the motor-generator. In other words, the first and secondsensors are configured to determine a change between an operationalstate in which the belt 202 is not slipping and another operationalstate in which the belt 202 is slipping. It may be appreciated, however,that the first and second sensors may be configured to determine adegree of change in the second and/or third operational states of thefirst and second movable portions 206, 208 owing to incremental changesin the operational torque of the motor-generator.

In one example, the tension in the belt 202, and hence the extent of themovement of the first and second movable portions 206, 208, may bedependent upon to the operational torque of the motor-generator. Assuch, the second and/or third operational states of the first and secondmovable portions 206, 208 may comprise a range of positions. In anotherexample, the degree of strain in the first and second movable portions206, 208 may be dependent upon the operational torque of themotor-generator. As such, the second and/or third operational states ofthe first and second movable portions 206, 208 may comprise a range ofstrain values.

Turning now to FIG. 6, an example operating routine 600 for a belt slipmonitor system is shown. The belt slip monitor system may include a beltslip monitor as described in FIGS. 2A-3B, and a belt coupled to an ISG,such as belt 202 in FIG. 2A.

At 602, the method may estimate engine and/or operating conditions. Theengine conditions may include, for example, engine speed, engine load,operational torque, etc. The engine conditions may be measured and/orestimated.

At 604, the method may determine the mode of operation. In a first modeof operation, a motor-generator, for example the one depicted in FIG. 1,is operating as a motor, wherein a secondary torque is applied in orderto assist in driving the belt, which may be belt 202, for example. In asecond mode of operation, the motor-generator is operating as a motor,wherein a resistive torque is applied to the belt.

At 606, the method may determine and/or monitor the operational statesof the first and/or second movable portions of the belt slip monitor asdepicted in FIGS. 2A-3B, for example. This may be done in part bysensors, as shown in FIGS. 3A and 3B, for example. In one example, thefirst and second movable portions of the belt slip monitor may comprisea first and second sensor, respectively. These sensors may be anglesensors, strain sensors, or position sensors. For example, the anglesensors may be configured to determine an angular positions of the firstand second movable portions. In another example, the method maydetermine the operational state of a first movable portion of the beltslip monitor using a first sensor, wherein the first movable portion ismovable with respect to the motor-generator and may determine theoperational state of a second movable portion of the belt slip monitorusing a second sensor, wherein the second movable portion is movablycoupled to the first movable portion, the second movable portion beingcoupled to the belt such that the operational states of the first andsecond movable portions of the belt slip monitor are dependent upon thetension in the belt.

At 608, the method may determine whether the belt is slipping. In oneexample, the belt may slip if an operational or resistive torque issufficiently large. An indication that the belt is slipping may occur ifthe operational state of the first movable portion and/or second movableportion of the belt slip monitor is in an equilibrium position. Forexample, the movable portions may be in this equilibrium position when atension of the first side of the belt is equal to the tension of thesecond side of the belt, as depicted in FIG. 4B, for example. In anotherexample, the method may determine the belt is slipping by a change inthe operational states of the first and second movable portions.

At 610, the method may corroborate that the belt is slipping by, forexample, comparing the outputs from the first and second sensors. In oneexample, the method may comprise comparing the outputs from the firstand second sensors against a predetermined set of values or thresholdsto corroborate that the outputs are indicative of the belt slipping.

At 612, the method may adjust an operational or resistive torque basedon an indication that the belt is slipping. For example, torque demandthrough the belt may be reduced by adjusting the operational torque ofmotor-generator, engine, and/or accessory devices. Reducing the torquedemand through belt may result in a reduced belt tension. In this way,the method comprises adjusting operational torque for reducing belttension based on the operational states of the first and second movableportion of the belt slip monitor. Countermeasures may include inhibitingstart-stop events, using the motor-generator and/or starter motor toassist cranking the engine, inhibiting ISG functions that transmithigh-torque through the belt and/or setting a flag or a malfunctionindication light. Further, a controller, such as controller 20 in FIG.1, with non-transitory memory may have instructions to adjustoperational or resistive torque or enact a countermeasure based on anindication of the belt slipping.

Although in the examples above, reference is made to the operationaltorque of the motor-generator affecting whether belt slip occurs, it isequally the case that the operational torque of other componentsassociated with the belt 202, such as the engine crankshaft and/or oneor more accessory devices, may affect whether belt slip occurs. Thefirst and second movable portions 206, 208 and their respective sensorsmay thus also determine whether the belt 202 is slipping due to theoperational torque of these other components.

It will be appreciated by those skilled in the art that although thepresent application has been described by way of example and withreference to the one or more examples above, it is not limited to thedisclosed examples and that alternative examples could be constructedwithout departing from the scope of the present application as definedby the appended claims.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A belt slip monitor for a belt coupled to amotor-generator, the belt slip monitor comprising: a first movableportion movable with respect to the motor-generator; a second movableportion movably coupled to the first movable portion, the second movableportion being coupled to the belt such that operational states of thefirst and second movable portions of the belt slip monitor are dependentupon a tension in the belt; a first sensor configured to determine theoperational state of the first movable portion; and a second sensorconfigured to determine the operational state of the second movableportion, wherein the belt slip monitor is configured to determinewhether the belt is slipping based on the operational states of thefirst and second movable portions.
 2. The belt slip monitor of claim 1,wherein the belt slip monitor is configured to determine if the beltcoupled to the motor-generator is slipping.
 3. The belt slip monitor ofclaim 2, the belt slip monitor further comprising one or more controldevices configured to adjust an operational torque of themotor-generator in response to the operational state of the first and/orsecond movable portion of the belt slip monitor, such that the belt doesnot slip.
 4. The belt slip monitor of claim 1, wherein the secondmovable portion is coupled to the belt at a first end of the secondmovable portion and is coupled to the belt at a second end of the secondmovable portion.
 5. The belt slip monitor of claim 4, wherein the firstand second ends of the second movable portion are coupled to the belt oneither side of the motor-generator.
 6. The belt slip monitor of claim 1,wherein the tension in the belt is dependent upon an operational torqueof the motor-generator.
 7. The belt slip monitor of claim 1, wherein atleast a portion of the first sensor is attachable to the first movableportion and at least a portion of the second sensor is attachable to thesecond movable portion.
 8. The belt slip monitor of claim 1, wherein thefirst movable portion is coupled to an anchor point that is fixedrelative to movement of the motor-generator.
 9. The belt slip monitor ofclaim 1, wherein the first and second movable portions are configured tomove with respect to the belt.
 10. The belt slip monitor of claim 1,wherein the first and second movable portions are rotationally and/orslidably movable.
 11. The belt slip monitor of claim 10, wherein thefirst and second movable portions are rotationally and/or slidablycoupled to each other, and wherein the second movable portion comprisesone or more pulleys for engaging the belt.
 12. The belt slip monitor ofclaim 1, wherein the belt slip monitor is configured to apply apretension to the belt.
 13. The belt slip monitor of claim 1, whereinthe first and second sensors comprise angle sensors configured todetermine an angular position of the first and/or second movableportion.
 14. The belt slip monitor of claim 1, wherein the first andsecond sensors comprise strain gauges configured to determine a strainin the first and/or second movable portion, and wherein themotor-generator comprises an integrated starter-generator.
 15. The beltslip monitor of claim 1, wherein the first and/or second movableportions are coupled to an engine of a vehicle, wherein the belt is anaccessory drive belt.